Electromagnetic brake for motor road-vehicles



G. POLLARD.

ELECTROMAGNETIC BRAKE FOR MOTOR ROAD VEHICLES.

' APPLICATION FILED OCT. I4. I918.

1,328,966. Patented Jan. 27,1920.

2 SHEETS-SIHEET I.

I I IND II! I] I I I I [til I I I v f I G.- POLLARD.

ELECTROMAGNETIC BRAKE FOR MOTOR ROAD VEHICLES.

APPLICATION FILED. OCT. 14, 19H

Patented Jan. 27,1920.

2 SHEETS-SHEET 2- nwlll um P UNITED sTATEs PATENT OFFICE.

GEORGE POLLARD, OF LONDON, ENGLAND, ASSIGNOR TO THE MENCO-ELMA SYNDICATE LIMITED, LONDON, ENGLAND.

ELECTROMAGNETIC BRAKE FOR MOTOR ROAD-VEHICLES.

Specification of Letters Patent.

Patented Jan. 27, 1920.

Application filed October 14, 1918. Serial No. 253,088.

To all whom. itmay concern:

Be it known that I, GEORGE POLLARD, a subject of the King of England, residing in London, England, have invented certain new and useful Improvements in Electiomagnetic Brakes for Motor Road-Vehicles,

, of which the following is a specification.

the co-acting members of electro-magnetic:

clutches when they engaged one another merely frictionally, was obviated- (see for instance the electro-magnet 16, flange 33 constituting its armature, and the projections 17 and 18 constituting a dog-clutch or brake, in Figure l of the drawings appended to the specification of prior British Letters Patent No. 19755 of 1914 granted to George Pollard and The Menco-Elma Syndicate Limited, and see the non-slipping electromagnetic clutches and brakes in the specifications of British Letters Patent Nos.

18,377 of 1914 and 10,539 of 1915, both granted to George Pollard and The Menco- Elma Syndicate Limited) but these non-slipping electro-magnetic clutches and brakes although they were advantageous in that they could not slip, were disadvantageous struction for a change-speed gear that is provided with co-acting clutch-members or brakemembers toothed or otherwise so shaped that when engaged they cannot be relatively rotated and made to slip, of the combination of such co-acting clutch-members or brake-members with an armature fixed to one member and an electro-rnagnet fixed to the other, the armature and electromagnet being characterized by a formation such that they have opposing faces parallel or approximately, so to the path in which they move in relation to one another in the operation of bringing the members into engagement. The purpose of making the said opposing'faces parallel, or approximately P so, is that the airfgap measured perpendicularly to those faces, shall be of less width than the distance through which they are relatively movable in the o eration of engaging or of disengaging t e said clutchmembers. By-tlieemployment of the present invention with theair-gap reduced as described in relation to the range of movement of the clutch or brake members, the ,clutch or brake fca'n beoperated with ease and certainty byi an electro-magnet that is much smaller and lighter, much less expensive, and requires much less'current than the electro-magnetic"dog-clutches and brakes of the aforesaid earlier specifications.

In the accompanying drawings Fig. .1 'is a verticalcentral section of part of the upper half of a change-speed gear of the type llustrated in the drawings appended to prior British s ecifications Nos. 18,337 of 1914 and 10,539 0 1915 aforesaid; it shows a dog-brake with one form of electro magnet applied thereto according to the present invention; and

Fig. 2 is aviewsimilar to Fig. 1 except that it has a different form of electrmnmg'net applied to it according to the present in vention.

Like referencei letters indicate like parts throughout the drawings.

With referenct first to Fig. 1, the gear comprises a shaft A and arms B, the arms intersecting the shaft and being fixed thereto, but not at right angles. The arms B in the example illustrated lean from the shaft A toward the flywheel F. The arms B receive motion from the motor (which motor actuates the shaft A carrying the fly-wheel F) and transmit this motion to the driven shaft A as a direct drive and at five other speeds in forward running, and also trans: mit a single reverse speed. and effect the braking of the vehicle. The manner in which the gear as a whole is arranged to give these variations of speed is not of the present invention, but is explained in the earlier British specifications Nos. 18,337 of 1914 and 10,539 of 1915.

- In the construction illustrated in Fig. 1,

the armature H of the electro-magnet H is arranged to slide in grooves 9 formed in the flange of the disk H which is virtually art of the wheel H the armature engaging with these grooves by means of radial projections p upon it parallel with the axis of the gear. Upon the part HR of the armature H are teeth 1". Opposed to the teeth 1" are teeth It fixed on the side of the electro-magnet H. The teeth 0" and the teeth It constitute co-acting'brake members fixed to the armature and to the electromagnet respectively, and the armature and electro-magnet, both cylindrical, are characterized by a formation such that they have opposing faces 7 f respectively, which -are annular andare parallel to the path,

' I indicated by the dimension D, in which they move in the operation of bringing the brake members 1" and 71. into engagement, and are separated by an air-gap whlch measured 1 perpendicularly to the faces, is of a dimension at, much less than the distance D aforesaid. Though the distance D through which the co-ac'ting dog-tooth members 7" and h of the brake have to be relatively moved tobringthe brake into action is the same as it would have to be in any similar dog-brake yet the air-gap d is obviously much reduced in relation thereto.

In Fig. 2 the. electro-magnet H is annular, with poles w and y between which is anannular recess into which the ring-armature H extends as shown when the brake is free, extending further into the annular recess when the brake is engaged. Teeth 1' and h, as in the former case are fixed to the armature H and magnet H respectively. In this case, as in the former, the dimension 0! is constant and is much less than the dimension D.

In the two cases chosen for illustration in the drawings the parts H and H? are provided with springs s which tend to keep the brake disengaged and which are overcome by the magnetic pull when the brake is to be brought into engagement. Also,

in the same two cases the electro-magnet E I is one which is carried on a rotating part (F) and the electro-magnet H is one which is carried on a fixed part (the casing X) as in the change-speed gears of the aforesaid prior specifications.

Fixed in the part HR of each armature H- are pins such as 1 on which the armature E of the electro-magnet E can slide as is usual against the action of a spring;

this is not of the present invention.

The present invention is applicable to any suitable electromagnetic clutch or brake in a change-speed gear when. the

clutch or brake is provided with co-acting clutch-members so shaped that When engaged they cannot be relatively rotated.

I am awarethan an armature and electro-magnet with opposing faces parallel or approximately so to the path in which they move in relation to one another in the operation of a clutch or brake are. not of them-- selves new, and I make no claim to them.

What I claim as m invention and desire to secure by Letters atent is In a change-speed gear of the epicyclic type, the combination with a rotatable driving wheel, a rotatable member journaled coaxially with the latter and adapted to be rotated thereby, and a fixed annular electromagnet which is coaxial with the driving wheel and has lateral teeth, of a driven wheel which is journaled coa-xially with said driving wheel and has an annular flange coaxial with the annular pole-face of said electromagnet, and a spring-controlled annular a rmature which is slldable on said flange in a direction parallel with the axis of the driving wheel, engages the flange to rotate therewith, engages the said member slidably in a direction parallel to said axis, is provided with teeth arranged to engage the former teeth, and has a cylindrical face that is arranged in close operative relation to the annular pole-face of the electroma net in all positions of the armature, for the purpose specified.

In testimony whereof I afiix my signature. 

